a) Peafowl study : Field study of peafowl mating behavior was conducted in Izu Cactus Park, Shizuoka Prefecture. We measured 1) male mating success ; number of copulation and hoot-dush behavior, 2) males' secondary sexual traits ; number of eye-spots and its asymmetry, and 3) intestinal parasite ; number of nematode eggs and protozoa oocytes. In results, fluctuating asymmetry (FA) in eye-spots negatively correlate with male mating success and with male parasite resistance. Number of eye-spots itself did not correlate with mating success. As females visited several males before copulation and male did not force to copulate with females, females seemed to choose healthier mates using FA indicator. We presented these results at International Behavioral Ecology Meeting, Nottingham, and Japan Ethological Society Meeting, Osaka.b) Human study : We investigate human mate choice behavior through literature. M.Hasegawa translated two influential English books of the area into Japanese : Helena Cronin "The ants and the peacocks : Altruism and sexual selection from Darwin to today" (Cambridge Univ.Press, 1991) and Matt Ridley "The red queen : Sex and the evolution of human nature." (Viking, Penguin, 1993) . She also contributes articles on human nature and sexual behavior through Japanese newspapers and magazines.